Controllable vibration generator

ABSTRACT

A vibration generator comprises two unbalance shafts, which are positively coupled in a contra-rotative manner and whose relative phrase position can be shifted by a phase shifting device. Each of the unbalance shafts supports a main unbalance mass and a partial unbalance mass that can move in relation thereto. The position of the partial unbalance masses on the respective unbalance shafts can be actively altered within a large range by adjusting devices. The resulting vibration vector generated by the vibration generator can set in a diverse manner with regard to direction and magnitude.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a vibration generator in accordance with thepreamble of claim 1.

2. Description of the Related Art

Such vibration generators are used advantageously for example inground-compacting machines, such as for example vibration plates, andare known from EP 0 358 744 B1.

In the case of the known vibration generators two unbalanced shafts arecoupled together in such a manner as to be able to rotate in oppositedirections, wherein their relative phase position can be adjusted bymeans of a phase changing device. Each of the unbalanced shafts supportsan unbalanced part which is rigidly attached to the respectiveunbalanced shaft, and an unbalanced part which can freely rotate on therespective unbalanced shaft over a predetermined angle range between endpositions which are limited by stops. The stops are disposed withrespect to the rigid unbalanced part in such a manner that the resultingtotal unbalance of the rigid unbalanced part and the movable unbalancedpart is a maximum value in the one end position of the movableunbalanced part and is a minimum value in the other end position. Thechange of position of the rotatable unbalanced parts between the two endpositions is effected by virtue of the fact that the direction ofrotation of the unbalanced shafts is reversed, i.e. that the rotatableunbalanced parts always assume the same end position in dependence uponthe direction of rotation of the unbalanced shaft which supports them.

The relative adjustment between the fixed unbalanced parts and themovable unbalanced parts changes in each case the effective resultingcentrifugal force and thus the so-called mr-value (product of theresulting unbalanced mass m and the radius r of the centre of gravity ofthe resulting unbalanced mass). When the rigid and the movableunbalanced part are disposed on the same side of the unbalanced shaft,their centrifugal forces are summated to create a high mr-value. If, onthe other hand, the movable unbalanced part is in its other end positionwith respect to the unbalanced shaft opposite the rigid unbalanced part,the mr-value is reduced to a minimum.

Such a vibration generator has proven itself extraordinarily well inpractice. However, a disadvantage has been established, in that in orderto adjust the movable unbalanced parts into the respective opposite endposition it is necessary to reverse the direction of rotation of theunbalanced shafts which represents a significant technical expenditurefor the drive of the unbalanced shafts. Furthermore, it is above alldesirable when using the vibration generator in ground-compactingmachines to be able to adjust the vibration generated by the vibrationgenerator in an optimum manner to suit the different grounds andground-compacting conditions even during the compacting process. Such afine adjustment of the vibration behaviour is not possible in the caseof the known vibration generators and definitely not during theoperation.

A generic type-forming vibration generator is known from DE-A-12 14 616,in which are provided a first adjusting device for adjusting the phaseposition between a main and a part unbalanced mass on a first unbalancedshaft and a second adjusting device for adjusting the phase positionbetween a main and a part unbalanced mass on a second unbalanced shaft,wherein the phase position can be adjusted between the first and thesecond unbalanced shaft by means of a phase changing device. The firstand the second adjusting device are coupled to each other by way ofplanetary gears, so that the adjustment of the phase position betweenthe main and part unbalanced mass on one unbalanced shaft causes acorresponding adjustment in the opposite direction of the phase positionof the unbalanced masses on the other unbalanced shaft.

The object of the invention is to provide a vibration generator, whosevibration parameters, in particular the vibration amplitude anddirection, can be adjusted freely and in a number of ways over wideranges.

The object is achieved by virtue of a vibration generator in accordancewith the invention according to claim 1. Advantageous furtherdevelopments of the invention are evident in the dependent claims.

OBJECTS AND SUMMARY OF THE INVENTION

In the case of the vibration generator in accordance with the inventionthere are disposed on the two unbalanced shafts in each case a mainunbalanced mass and a part unbalanced mass which moves relatively withrespect to the main unbalanced mass, wherein a first adjusting device isprovided for the purpose of actively adjusting the phase positionbetween the main unbalanced

In the case of the vibration generator in accordance with the inventionthere are disposed on the two unbalanced shafts in each case a mainunbalanced mass and a part unbalanced mass which moves relatively withrespect to the main unbalanced mass, wherein a first adjusting device isprovided for the purpose of actively adjusting the phase positionbetween the main unbalanced mass and the part unbalanced mass of thefirst unbalanced shaft and a second adjusting device is provided foractively adjusting the phase position between the main unbalanced massand the part unbalanced mass of the second unbalanced shaft, and theadjusting devices and the phase changing device which determines thephase position of the two unbalanced shafts are supplied with energyfrom an external source and in each case comprise a separate control.The adjusting devices render it possible for almost any desired phasepositions to be set between the main unbalanced mass and the partunbalanced mass. Since the adjusting devices are actively effective, itis not necessary to reverse the direction of rotation of the unbalancedshafts—as is the case for example in the prior art. Furthermore, thechange in the phase position is not only limited to two end positionsdetermined by stops. If the adjusting devices are controlledindependently of each other, it is also possible to set a differentphase position between the main unbalanced mass and the part unbalancedmass on the first unbalanced shaft than on the second unbalanced shaft.Also, as a consequence, it is possible in numerous ways to setpredetermined vibration patterns which can be used advantageously forexample for the purpose of ground compacting. Since, as a result, theadjusting devices and the phase changing device can be actuatedindividually, it is possible to set an almost infinite number ofvibration patterns, i.e. in particular amplitudes and resultingvibration directions.

In the case of a different advantageous embodiment of the invention thefirst adjusting device and the phase changing device are in factsupplied with energy from an external source and can be controlledindividually in each case. However, the second adjusting device does notcomprise its own external energy supply and is controlled by way of theeffect of the phase changing device alone or the first adjusting deviceand the phase changing device. In an advantageous manner the control isperformed by means of a form-locking coupling arrangement, so that anadjusting effect by means of the first adjusting device or by means ofthe phase changing device also directly causes an adjusting effect ofthe second adjusting device. In contrast to the above describedadvantageous embodiment this means that the adjustment range is nolonger as wide as the second adjusting device cannot be controlledindividually. On the other hand, however, by coupling it to the firstadjusting device and/or the phase changing device the advantage iscreated that it is extremely convenient to synchronise the movements, inparticular to synchronise the adjustment of the part unbalanced massesto the associated unbalanced shafts and no special control procedure isrequired by the operator to synchronise the adjustments. Thus, it is notnecessary, as is possibly the case in the above described embodiment, tosynchronise the control for the adjusting devices for the purpose ofsetting the part unbalanced masses in phase on the associated unbalancedshaft.

In the case of a particularly advantageous embodiment of the inventionthe part unbalanced masses can rotate relatively with respect to themain unbalanced masses whilst controlling the corresponding adjustingdevice and engage over the main unbalanced masses in the form of halfshells.

It is particularly advantageous if the adjusting devices and the phasechanging device in each case render it possible to change continuouslyas desired the respective phase positions and subsequently to fix saidphase positions. The fixing of the phase position ensures that avibration behaviour of the vibration generator which has been set onceby the operator and a resulting relative position of the unbalancedshafts and the unbalanced masses carried by said shafts is alsomaintained constant over a longer period of time.

If the phase positions can be changed in a range of up to 360° anydesired vibration direction and amplitude can be set within the scope ofthe limit values determined by the mechanical structure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the invention are furtherexplained hereinunder with the aid of the accompanying drawings, inwhich:

FIG. 1 shows a schematic section in the plan view of a vibrationgenerator in accordance with the invention according to a firstembodiment;

FIG. 2 shows a diagram for explaining different relative positions ofunbalanced shafts and unbalanced masses in the case of the firstembodiment of the invention;

FIG. 3 shows a schematic sectional view in the plan view of a vibrationgenerator according to a second embodiment of the invention; and

FIG. 4 shows a diagram for explaining the relative positions ofunbalanced shafts and unbalanced masses in the case of the secondembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a first embodiment of the invention in a plan view.

A first unbalanced shaft 2 and a second unbalanced shaft 3 are rotatablymounted in an generator housing 1. The first unbalanced shaft 2 isrotatably driven by a motor 4, for example an electric or hydraulicmotor. The rotational movement of the first unbalanced shaft 2 istransmitted in a form-locking manner by way of mutually meshing toothedwheels 5, 6 to the second unbalanced shaft 3 which as a result rotatesin the opposite direction with respect to the first unbalanced shaft 2.

A phase changing device 7 is provided on the second unbalanced shaft 3in the flow of force of the form-locking arrangement between the firstunbalanced shaft 2 and the second unbalanced shaft 3, which phasechanging device renders it possible to change the relative phaseposition between the first and the second unbalanced shaft 2, 3.

A component of the phase changing device 7 is a hub 8 which is formed onthe toothed wheel 6 and comprises on its inner side one, preferably two,screw-like groove(s) 9 which extend in a substantially inclined manner.

The phase changing device 7 is also associated with a piston 10 whichcan be actuated axially in a hydraulic manner and which can likewisemove a guide element 12 in an axial direction by way of a piston rod 11.The guide element 12 supports a pin 13 which extends perpendicular tothe rotational axis of the second unbalanced shaft 3. In the region ofthe pin 13 the second unbalanced shaft 3 is formed as a hollow shaft andis provided with opposite-lying, mutually parallel slots 14 which extendin parallel with the direction of the axis and which penetrate the wallof the shaft. The length of the slots 14 corresponds substantially tothe axial extension of the screw-like groove 9 in the toothed wheel 6.The pin 13 penetrates the slots 14 and extends as far as into the groove9, or possibly into two opposite grooves 9.

The piston 10 is hydraulically controlled by the operator or by acorresponding control device. As an alternative thereto, it is alsopossible to control the piston 10 by means of a pneumatic control, anelectric motor or an electromagnet control.

Whereas the piston 10 comprising the piston rod 11 is non-rotatablyconnected to the generator housing 1, the guide element 12 and the pin13 rotate with the second unbalanced shaft 3. Accordingly, a roller orslide bearing is provided for the purpose of uncoupling the movements.

When the piston 10 is axially displaced with the piston rod 11 and theguide element 12, the pin 13 also moves in an axial manner. It is notpossible for the pin 13 to rotate relatively with respect to the secondunbalanced shaft 3 as it is guided in the slots 14. Owing to thescrew-like progression of the grooves 9 in the toothed wheel 6 thetoothed wheel 6, which cannot be displaced in an axial manner, rotatesrelatively with respect to the second unbalanced shaft 3. However, asthe toothed wheel 6 is coupled directly in a form-locking manner by wayof the toothed wheel 5 to the first unbalanced shaft 2, the phaseposition between the two unbalanced shafts 2, 3 is consequently changed.This principle is known from EP 0 358 744 B1 and therefore does notrequire any further explanation.

Each of the unbalanced shafts 2, 3 supports a main unbalanced mass 15illustrated only schematically in FIG. 1 and a part unbalanced mass 16which can rotate on the respective unbalanced shaft 2, 3 relatively withrespect to the main unbalanced mass 15 and which engages in the form ofa half-shell over the main unbalanced mass 15.

The rotation of the part unbalanced masses 16 on the associatedunbalanced shafts 2, 3 and thus a change in the phase positions betweenthe main unbalanced masses 15 and the associated part unbalanced masses16 is achieved on the first unbalanced shaft 2 by means of a firstadjusting device 17 and on the second unbalanced shaft 3 by means of asecond adjusting device 18. The part unbalanced masses 16 are held onthe unbalanced shafts 2, 3 by means of slide bearings.

The adjusting devices 17, 18 function according to the same principle asthe phase changing device 7, so that reference is made to thedescription thereof already provided and for the purpose ofsimplification the same designation numerals are used. By controllingthe piston 10 of the first adjusting device 17 or the second adjustingdevice 18 respectively the associated part unbalanced mass 16 can berotated relatively with respect to the associated main unbalanced mass15 in a range of up to 180°.

FIG. 1 illustrates a case where the part unbalanced masses 16 are heldby means of the adjusting devices 17, 18 in a position in which they arelocated with respect to the axes of rotation of the unbalanced shafts 2,3 on the same side as the main unbalanced masses 15. Accordingly, thecentrifugal forces are summated to form a resulting great total forcewhich can lead to a strong vibration movement and thus compacting powerof a ground-compacting machine using the vibration generator.

When the two adjusting devices 17, 18 are actuated simultaneously it canbe achieved that the part unbalanced masses 16 are pivoted to a side ofthe unbalanced shafts 2, 3 lying opposite the main unbalanced mass 15,so that their centrifugal forces are directed in the opposite directionto the centrifugal forces of the main unbalanced masses 15. Accordingly,the resulting total force is low, which can be expedient for exampletowards the end of a compacting procedure or also for the purpose ofprotecting a ground which has already been compacted.

FIG. 2 illustrates a diagram with different relative positions of theunbalanced shafts 2, 3 which are, above all, relevant in practice andthe respective associated main unbalanced masses 15 and part unbalancedmasses 16. FIG. 2 also illustrates in each case only end or maximumpositions of the phase changing device 7 or the adjusting devices 17,18.Naturally, an almost infinite number of intermediate positions arepossible. The schematically illustrated unbalanced shafts 2, 3 areillustrated in the form of a perpendicular section of FIG. 1.

It is to be noted that the unbalanced shafts 2, 3 rotate in oppositedirections and accordingly only instantaneous recordings can beillustrated. A large arrow represents a resulting great total force withunbalanced masses 15, 16 lying on the same side, whereas a small arrowrepresents a resulting small force with opposite-lying unbalanced masses15, 16.

Depending upon the adjustment of the phase changing device 7 thedirection of the resulting total force generated by the vibrationgenerator can be changed, so that as desired a direction of vibrationcan be set in the rearwards or forwards direction as well as a verticaldirection of vibration. Vibration in the vertical direction does notgenerate any horizontal force component which could possibly move avibration plate in the corresponding direction.

When using the vibration generator in a vibration plate the phasechanging device 7 for the forwards and rearwards movement of thevibration plate is actuated. The resulting force vector from the twounbalanced shafts is adjusted accordingly in its direction.

In the case of a synchronised, i.e. identical direction, actuation ofthe adjusting devices 17, 18 and with suitable pitch directions of thegrooves 9 the mr-value is set by means of the relative pivot of the partunbalanced masses 16, without the phase position of the resulting forcevector changing. In the case of a one-sided or uneven, non-synchronisedactuation of the adjusting devices 17, 18, the mr value of theindividual unbalanced shafts 2, 3 changes. A change in the phaseposition of the resulting total centrifugal force vector in size anddirection likewise occurs as a consequence, which offers a large rangeof possible adjustments.

FIG. 3 illustrates a second embodiment of the invention in a schematicsection in plan view.

For the purpose of simplification only the differences between thesecond embodiment and the above described first embodiment are explainedhereinunder so that components which remain unchanged with respect tothe first embodiment are designated with like numerals.

The essential difference with respect to the first embodiment resides inthe design of the second adjusting device (now designation number 19).Whereas the second adjusting device 18 of the first embodiment can beindividually controlled and likewise supplied with energy from anexternal source by means of hydraulic power supplied from an externalsource, as is the first adjusting device 17, the second adjusting device19 of the second embodiment does not have a separate energy supply froman external source and also cannot be controlled individually.Furthermore, the adjusting device 19 is no longer used to adjust thephase between the part and the main unbalanced mass 15, 24 but rather toadjust the phase position between the part unbalanced mass 16 of thefirst shaft and the part unbalanced mass 24 of the second shaft.

This is achieved by virtue of the fact that the second adjusting device19 comprises a toothed wheel 20 which meshes with a toothed wheel 21attached to the part unbalanced mass 16 of the first unbalanced shaft 2.

In contrast to the first embodiment, a second unbalanced shaft 22 is notfully mounted in the generator housing 1. On the contrary, one end sideof the said second unbalanced shaft adjoins a freely rotatably partshaft 23, wherein the second unbalanced shaft 22 and the part shaft 23are connected by means of a roller bearing 23 a and form one unit whichfor its part is mounted in the generator housing 1.

A part unbalanced mass 24 which can rotate about the second unbalancedshaft 22 is fixedly connected to the part shaft 23. Moreover, the partunbalanced mass 24 surrounds the main unbalanced mass 15 in the samemanner as is the case in the first embodiment.

The part shaft 23 is formed as a hollow shaft and comprises two slots 25which lie in parallel opposite each other, extending in parallel withthe direction of the axis. The slots 25 are penetrated perpendicular tothe direction of the axis by a pin 26 which engages in screw-likegrooves 27 which are formed in the hub of the toothed wheel 20. Thegrooves 27 extend on the inner side of the hub of the toothed wheel 20with an axial extension which corresponds to the axial length of theslots 25.

The pin 26 is held by a guide element 28 which is connected by means ofa piston rod 29 to the guide element 12 of the phase changing device 7in a manner which can be uncoupled by rotation but which is nonethelessform-locking.

The toothed wheels 20, 21 and the toothed wheels 5, 6 have an identicaldiameter.

The mode of function of the second embodiment is explained hereinunder.

Upon actuating the first adjusting device 17 for the purpose of changingthe phase position of the part unbalanced mass 16 on the firstunbalanced shaft 2 the corresponding pivot movement is transmitted byway of the toothed wheel 21, the toothed wheel 20, the grooves 27 andthe slot 25 to the part shaft 23 and thus finally to the part unbalancedmass 24 of the second unbalanced shaft 22. The part unbalanced mass 24is thus pivoted in a similar manner to the part unbalanced mass 16 ofthe first unbalanced shaft 2. It is thus not necessary to synchronisethe movements. However, it is consequently also not possible to adjustindividually the phase position of the part unbalanced mass 24 on thesecond unbalanced shaft 22.

Upon changing the phase position between the first unbalanced shaft 2and the second unbalanced shaft 22 by actuating the phase changingdevice 7 the piston 10 is displaced axially which causes a correspondingaxial displacement of the pins 13 and 26. Accordingly—as alreadyexplained in connection with the first embodiment—the associated toothedwheels 6 and 20 are pivoted relatively with respect to the secondunbalanced shaft 22 or the associated part shaft 23 so that overall thephase position with respect to the first unbalanced shaft 2 changes.

Different possible adjustments in the case of the second embodiment areillustrated schematically in FIG. 4. Also in this case a large arrowmeans that the main and the part unbalanced mass are located on the sameside and thus generate a resulting large vibration amplitude, whereas asmall arrow corresponds to an opposite-lying arrangement of theunbalanced masses and thus to a resulting low vibration amplitude.

An actuation of the first adjusting device 17 in the case of the secondembodiment causes the same change of the mr-value for the two unbalancedshafts 2, 22, without the phase position of the resulting force vectorbeing changed.

The adjusting devices 17, 18, 19 and the phase changing device 7 can becontrolled in a mechanical, hydraulic or electric manner. It is readilypossible to use upstream corresponding control algorithms which renderit easier to operate the vibration generator. In this case it isexpedient to provide in addition an angle of rotation sensor, a positionsensor, position or path sensors, an acceleration recorder etc. for thepurpose of determining the respective characteristic variables.

In the case of further embodiments not illustrated in the figures it ispossible to change the arrangement of the components and the manner inwhich components cooperate without deviating from the basic principle ofthe invention. Thus, for example in the case of the first embodimentaccording to FIG. 1 it is possible to exchange the phase changing device7 and the motor 4 in the arrangement so that the motor 4 drives thesecond unbalanced shaft 3.

1. A vibration generator comprising: a first unbalanced shaft and asecond unbalanced shaft which is axially parallel to the firstunbalanced shaft and which is coupled thereto by a form-locking couplingsuch that the first and second unbalanced shafts can rotate in oppositedirections, one of the unbalanced shafts being driven to rotate; and aphase changing device which is integrated in the form-locking couplingbetween the first and second unbalanced shafts for the purpose ofadjusting a relative phase position of the first and second unbalancedshafts; wherein each of the first and second unbalanced shafts bears amain unbalanced mass and a part unbalanced mass which moves with respectto the main unbalanced mass; a first adjusting device is provided foractively adjusting phase position between the main unbalanced mass andthe part unbalanced mass on the first unbalanced shaft; wherein a secondadjusting device is provided for actively adjusting a phase positionbetween the main unbalanced mass and the part unbalanced mass of thesecond unbalanced shaft; the first adjusting device and the phasechanging device are supplied with energy from an external source and areeach controlled by a separate control, and the second adjusting deviceis coupled to one of the phase changing device and to a combination ofthe first adjusting device and the phase changing device in such amanner that it is controlled exclusively by way of the effect of thephase changing device or the combination of first adjusting device andthe phase changing device; wherein the second unbalanced shaft and themain unbalanced mass on the second unbalanced shaft are fixedlyconnected to each other; and wherein the second adjusting device iscoupled to the phase changing device in a form-locking manner such thatan adjustment, caused by the phase changing device, of the phaseposition of the first unbalanced shaft causes a similar adjustment ofthe phase position of the part unbalanced mass on the second unbalancedshaft.